1. Field of the Invention
The present invention relates in general to cycling helmets and, more particularly, to a structural improvement in such helmets not only for minimizing air resistance, but also for improving the appearance of the helmet by preventing the helmet chin strap from being exposed at the top of the helmet.
2. Description of the Prior Art
As well known to those skilled in the art, shock absorbers for cycling helmets are typically formed of styrofoam (polystyrene foam) or polyurethane foam.
A typical cycling helmet having an inner shock absorber made of styrofoam is shown in FIG. 1. In this helmet, the shock absorber is formed of styrofoam into the shape of the helmet. The above shock absorber forms a helmet body 10. A chin strap 11 is coupled to the helmet body 10 prior to covering the top of the body 10 with a thin PVC cap 12. After covering the body 10 with the cap 12, a bonding tape 13 is applied to the edge of the cap 12 so as to attach the cap 12 to the body 10.
That is, the above cycling helmet with the shock absorbing helmet body 10 of styrofoam is produced by attaching the separately formed PVC cap 12 to the helmet body 10 using the tape 13. In this type of helmet, the chin strap 11 is not exposed outside the helmet's top thereby being profitable in view of reducing the air resistance. However, the above helmet has a significant defect. That is, it is very difficult to securely attach the PVC cap 12 to the helmet body 10 using the tape 13. The cap 12 may be thus undesirably separated from the body 10 thereby not only causing rattling of the cap 12 on the body 10, but also increasing the air resistance while cycling.
In order to rectify the above problem, another type of cycling helmet having a helmet body of polyurethane foam has been proposed. This helmet is shown in FIG. 2. In order to produce this cycling helmet, a separately formed PVC cap 22 is placed in a mold prior to forming the helmet body 20 of polyurethane foam. While forming the helmet body 20 of polyurethane foam, the body 20 becomes integrated with the PVC cap 22 to form a single body. After forming the body 20, a chin strap 21 is coupled to the helmet. In this case, the strap 21 is partially exposed outside the top of the helmet.
An advantage of the above helmet resides in the fact that the cap 22 neither separates from the body 20 nor rattles on the body 20 since the cap 22 is integrated with the helmet body 20 into the single body while forming the body 20. However, this helmet is problematic in that the chin strap 21 is partially exposed outside the top of the helmet. When the chip strap 21 is exposed outside of the helmet, it will increase the air resistance.
The molding temperature of the polyurethane resin used for forming the body 20 is from 35.degree. C. to 40.degree. C. In order to form the helmet body 20, the separately formed PVC cap 22 is first placed in a bottom mold.
After placing the cap 22 in the bottom mold, the polyurethane resin is charged into the bottom mold. Thereafter, the bottom mold is airtightly closed by a top mold, thus forming a mold assembly.
The mold assembly with both the cap 22 and the polyurethane resin in turn pass through a heat chamber heated to about 55.degree. C.-60.degree. C. While passing through the heat chamber, the polyurethane resin is foamed to form the helmet body 20 integrated with the PVC cap 22.
After forming the helmet body 20, the top mold is separated from the bottom mold prior to taking the helmet out of the mold assembly.